Download presentation
Presentation is loading. Please wait.
Published byMartin Robinson Modified over 9 years ago
1
7000A GC-QQQ Applications Pesticides in Foods (1)
2
Measuring Methamidophos in Garlic This application demonstrates the phenomenon called matrix-induced chromatographic response enhancement when analyzing trace components in complex matrices. The polar organophosphorus insecticide, methamidophos, a metabolite of acephate is a difficult compound to quantitate in foods due to its polar nature and very early elution in GC analyses.
3
GC-QQQ Full Scan Spectrum Methamidophos Spectrum from Nist05 Methamidophos Spectrum by GC-QQQ
4
Methamidophos Calibration Curve (5, 10, 50,100ppb Solvent only)
5
Matrix Effect in Garlic Spike (ppm)Calc. (ppm) 10.0050.0187 20.010.0449 30.050.285 40.100.522 Methamidophos All the calculated results are much higher than spiked even though linearity is very good. The is due to the “matrix effect”.
6
Matrix Effect and Protectants A common problem in gas chromatography (GC) applications is the analyte losses and/or peak tailing due to undesired interactions with active sites in the inlet and column. Analytes that give poor peak shapes or degrade have higher detection limits, are more difficult to identify and integrate, and are more prone to interferences than stable analytes that give narrow peaks. For susceptible analytes, significant peak quality improvements are obtained when matrix components are present because they fill active sites, thus reducing analyte interactions. This phenomenon is called matrix- induced chromatographic response enhancement. Analyte protectants are added to both sample extracts and calibration solutions. For this analysis the analyte protectant solution contained 3-ethoxy-1,2-propandiol and sorbitol.
7
Methamidophos 5 ppb in solvent without and with protectant No protectant No methamidophos With protectant, it’s there (Due to the protectant, R.T shifts)
8
Methamidophos 10 ppb in Garlic without and with protectant Without protectantWith protectant Area:7084Area:9442
9
Methamidophos Calibration Curve (5, 10, 50,100ppb with Protectant)
10
Outstanding Accuracy in Garlic Spike (ppm)Calc. (ppm) 10.0050.0054 20.010.0127 30.050.067 40.100.116 Methamidophos
Similar presentations
© 2025 SlidePlayer.com Inc.
All rights reserved.